Electron transfer in Cobalt complexes using rigid ferrocenyl decorated polypyridyl based ligands

电子转移过程是许多化学反应中的重要步骤。这些过程在非常不同的时间尺度上进行。在这个项目中，将合成异双金属配合物，氧化后将发现分子内电子从钴(II/III)离子转移到二茂铁基取代基。所采用的钴离子周围的十六酸盐配体一方面形成稳定的钴(II)络合物，具有较高的氧化为钴(III)络合物的活化势垒，另一方面自由反应能较低。由于这些性质，配合物可以在两个相互转化缓慢的亚稳态中被发现。钴配合物的配体球体内的巨大结构变化稳定了这两个态，使它们在相当的高温下可以并排观察到。这两个态都可以通过温度变化或光照射等外部刺激来寻址，使这些分子在数据存储和分子开关方面的应用变得有趣。引起人们高度关注的是伴随着电荷转移诱导的自旋转移(CTIST)的MMCT吸收(金属到金属电荷转移)的可能发生，它允许通过光的照射来诱导电子转移。电子转移过程将通过电化学、核磁共振和电子自旋共振光谱以及UV/VIS/NIR光谱的手段进行详细的研究。

Electron transfer processes are important steps in many chemical reactions. These processes proceed on very different time scales. Within this project hetero bimetallic complexes will be synthesized, after oxidation an intramolecular electron transfer will be found from a cobalt(II/III) ion to a ferrocenyl substituent. The employed hexadendate ligand around the cobalt ion is chosen that: on the one hand stable cobalt(II) complexes are formed, with high activation barrier for the oxidation to the cobalt(III) complex and on the other side the free reaction energy is low. Due to these properties the complex can be found in two metastable states that interconvert slowly.The large structural changes within the ligand sphere of the cobalt complexes stabilize the two states making them observable side by side at comparable high temperatures.Both states might be addressable by external stimuli like temperature change or light irradiation, making these molecules interesting for applications in data storage and molecular switches. Of high interest is the possible occurrence of an MMCT absorption (Metal to Metal Charges Transfer) accompanied with CTIST (Charge Transfer Induced Spin Transition) which allows inducing an electron transfer by irradiation of light.The electron transfer process will be studied in detail by means of electro chemical, nuclear and electron spin resonance spectroscopy as well as UV/Vis/NIR spectroscopy.